Foamable vinyl resin composition containing polyhalogenated hydrocarbon and process for producing cellular structure therefrom



United Stats Patent FOAMABLE VINYL RESIN COMPOSITION CON- TAININGPOLYHALOGENATED HYDROCAR- BON AND PROCESS FOR PRODUCING CELLU- LARSTRUCTURE THEREFROM Dewey D. Lineberry, Louisville, Ky., assignor, bymesne assignments, to Union Carbide Corporation, New York, N.Y., acorporation of New York No Drawing. Continuation of applications Ser.No. 541,063 and Ser. No. 541,064, Oct. 17, 1955. This application June11, 1959, Ser. No. 819,546

28 Claims. (Cl. 260-25) This invention relates generally to theproduction of formed vinyl resin products and more particularly to animproved process for producing a cellular or porous structure in aplasticized vinyl resin from a plastisol of such resin.

Plastisols, as defined in the art and as employed herein, arecompositions containing finely divided polymer, generally of a vinylchloride resin suspended in a liquid organic plasticizer for thepolymer. At ordinary temperatures the resin particles are negligibly oronly very slightly soluble in the plasticizer and the compositions arefluid, but upon being heated to an elevated temperature the resinparticles undergo fusion and solvation in the plasticizer, and uponsubsequent cooling a plasticized solid resin results.

In the Schwencke patent, US. 2,666,036, issued January 12, 1954, forMethods of Producing a Cellular Structure in a Plasticized Vinyl EsterResin, a process is disclosed for producing a vinyl resin foam, bydispersing a low temperature boiling inert gas such as carbon dioxide,nitrous oxide, or helium in a vinyl resin plastisol. The process of thatpatent has come into considerable use; however, in that process it isnecessary that a relatively high gas pressure must be employed in thedispersing step, in most instances at least about 300 to 500 p.s.i.g.,in order to incorporate sufficient gas in the foam to produce theusually desired low density cellular structure in the fused foam.Pressures below 100 psi. cannot, however, be employed in the Schwenckeprocess. In order to produce a satisfactory low density foam forsubsequent fusion and solvation, atomizing spray devices utilizingadditional gas must be employed at the outlet of the high pressuredispersing zone.

During the spraying and forming of shaped foamed cellular structures bythe Schwencke process, about 90 percent of the gas is lost to theatmosphere and only about percent remaining to form cells. Consequently,large volumes of excess gas must be employed. This is undesirable inmany operations. In most commercial operations it has been found that inorder to disperse sufiicient gas into the plastisol, simultaneouschilling and violent mechanical agitation of the gas plastisol mixturemust be employed. This again generally requires special and expensiveequipment.

While various chemical blowing agents have been used heretofore toproduce an expanded cellular structure, these agents differ from thoseof the present invention by generating the foaming gas by decompositionor chemical reaction when the mass reaches the decomposition or reactiontemperature of the chemical agent. With such foaming agents the cellsare very suddenly formed and the use of closed molds is necessary toproduce a commercially attractive product.

It is a primary object of the present invention to pro vide a lowpressure process which is very eflicient from the standpoint of foamingagent utilization and which may, if desired, be carried out withoutatomizing or 3,052,643 Patented Sept. 4, 1962 spraying apparatus and ina simple open vessel or low pressure vessel equipped with an agitatorinstead of in a relatively. complex highly pressurized agitated chillingapparatus heretofore employed in the art.

It is another object of this invention to provide a foamable compositionwhich is free flowing before and after foaming .and which producescellular plasticized foam products superior to those previouslyavailable.

Other objects and advantages of the present invention will be obvious tothose in the art.

According to the present invention, it has now been discovered that bydispersing or dissolving certain inert polyhalogenated hydrocarbonliquids or gases in a vinyl resin plastisol, superior free-flowing fluidfoams are produced which may be flowed into molds or onto moving beltsor otherwise formed into desired shapes and can be fused by simple heattreatment to produce deformable, resilient rubber-like cellularproducts. Moreover, in this invention it is not critically necessary tochill the plastisol during the dispersing step or to resort to sprayingor atomization in order to produce low density cellular products. Thephysical structure of the fused foam of this invention is sponge-likewith superior quality to any heretofore produced. The fact that thefoaming agents of this process volatilize at a low temperature, at leastabout 150 F. below the plastisol fusing temperature, is quite important,for low temperature volatilization results in the formation of bubbleswithin the plastisol while the plastisol is still in a relatively fluidstate before solvation of the resin has occurred. This permits a greaterdegree of expansion of the material resulting in lighter foams and, ifdesired, in an open rather than closed cell structure, for as thetemperature rises to the fusing temperature the cell walls may readilybreak down between adjacent cells forming an interconnecting, open porestructure. Conversely, with chemical blowing agents which decompose toproduce gas at or near the fusing temperature when the resin isrelatively strong, closed cells usually result. The term cellularstructure in the following description and in the claims is used todescribe both the open, sponge-like interconnecting cell structure andthe non-interconnected cellular structures in which most of the cellsare closed.

The process of this invention and the compositions described herein aredirected to vinyl resin plastisols, i.e., a Z-phase system in which avinyl resin in small particulate form is dispersed and suspended in aplasticizer for the resin which has little or no solvating action ontheresin at room temperature but will dissolve the resin at elevatedtemperature and cause it to fuse into a plasticized structure. By theterms vinyl resins and vinyl chloride resins as used herein is meant toinclude the vinyl chloride homopolymers and the copolymers,interpolymers and terpolymers of vinyl chloride with other ethylenicallyunsaturated monomers, and mixtures of the homopolymers with other vinylchloride copolymers, interpolymers and terpolymers, and particularlythose vinyl chloride resins containing a predominant amount of vinylchloride polymerized therein, i.e., at least about 50 percent by weightand more. The preferred vinyl resins employed in this invention arethose containing from 60 to percent by weight of vinyl chloride inpolymeric form.

The ethylenically unsaturated monomers which can be polymerized withvinyl chloride to form the co polymers, interpolymers and terpolymersinclude, for example, lower alkyl unsaturated esters, particularly vinylacetate, partially hydrolyzed vinyl acetate, diethylmaleate,

.vinyl benzoate and the like, lower alkyl acrylates, such as methylacrylate, ethyl acrylate, butyl acrylate, octyl acrylate, and the like,as well as the corresponding methacrylates, alkyl esters of unsaturatedacids such as maleic and fiumaric acids, as well as othercopolymerizable com pounds as unsaturated nitriles, for example,acrylonitrile, halogenated hydrocarbons such as vinylidene chloride andfluoride, vinyl fluoride, chlorotrifluoroethylene and like compounds andother polymerizable compounds containing ethylenic unsaturation. Of thecopolymers, particularly preferred are the vinyl chloride-vinyl acetatecopolymers, particularly those containing 85 percent or more of vinylchloride polymerized therein.

The physical properties of the plastisol which is utilized have beenfound to be quite important. Ordinarily, plastisols are classified intothree groups according to viscosity. These having viscosities of lessthan 10,000 centipoises are generally considered low viscosityplastisols. The intermediate range is 10,000 to 50 ,000 centipoises, andplastisols with viscosities of 50,000 centipoises and above areconsidered to be high viscosity plastisols. Experience has shown thatboth the low and intermediate viscosity plastisols can generally alwaysbe satifactorily foamed by the process of this invention withsignificant ease. While certain of the high viscosity plastisols(frequently called pastes) are somewhat viscous for satisfactoryincorporation of the gaseous foaming agent, the use of normally liquidfoaming agents of this invention or of volatile thinners can lower theviscosity of these high viscosity plastisols for satisfactory foaming.Most generally, the vinyl resin plastisols are made having from 30 to 70weight percent of plasticizer, however, depending upon the desiredplasticity of the resultant foam and the viscosity of the plastisolsecured, greater or lesser amounts may be used.

In most instances emulsion polymerized stir-in type vinyl resins arepreferred to grinding-type because the larger particle size of thestir-in resins produces a lower viscosity plastisol with the same ratioof resin to plasticizer, and this ratio often is more or less fixed bythe properties desired in the fused foam. Generally, the higher theproportion of plasticizer, the less rigid the resultant foam will be.Stir-in resins which have an average particle size of about one to twomicrons are generally preferred because of ease in forming the plastisolin conventional mixing apparatus, but, by selecting appropriateplasticizers, viscosity within the critical range may usually beattained even though the resin particle size is considerably smaller.

When grinding-type resins are employed, it usually is desirable ornecessary to use a ball or pebble mill to break up the agglomeratedresin particles to a suflicient degree to form the dispersion. Withgrinding-type resins the particle size is usually much smaller, rangingfrom a few hundredths up to some larger fraction of a micron in averagesize, and the increased surface exposed to the solvent action of theplasticizer produces a less stable plastisol from a viscositystandpoint, for as solvation occurs at the resin-plasticizer interfaces,the viscosity increases. Of course, if the plastisol is to be made upfor immediate foaming and use, this partial solvation is notparticularly disadvantageous. Stir-in resins command -a somewhat higherprice than grinding types, but in most instances the higher price isjustified since the cost of grinding is saved and since the resultantplastisol may be held for a relatively long period of time prior tofoaming without the viscosity rise becoming excessive.

Any of the organic plasticizers for vinyl resins which have little or nosignificant solvating action on the vinyl resin at room temperatures canbe used in this invention.

7 Illustrative of some of the well known organic plasticizer are'tricresyl phosphate, dioctyl phosphate, phthalate plasticizers, such asdi-Z-ethylhexyl phthalate and other well known plasticizers or mixturesof two or more plasticizers. Generally speaking, the plasticizer shouldnot have a significant solvating action for the resin at roomtemperature at least until the plastisol is foamed, and it should alsohave sufiiciently low viscosity so as to produce a free flowing fluidplastisol, preferably one having a viscosity within the range of about5,000 to about 50,000 centipoises. The amount and kind of plasticizer isusually dictated by the properties desired in the fused foam, and, if arelatively stiif foam is desired, smaller quantities of a more fluidplasticizer may be employed as compared with larger quantities of a moreviscous plasticizer for softer foams. Of course, the density and cellsize of the foam also must be taken into account, but, because with thepresent invention it is possible to produce extremely light cellularproducts, there is much more latitude in the plastisol formulation thanwith the foaming process heretofore used.

Thus, as employed herein, the term fluid plastisol is meant to includethose plastisols of a vinyl resin and plasticizer in amounts providingfree-flowing features, i. e., pourable, paint-like mixtures, which canbe an admixture of just resin and plasticizer, or can be resin,plasticizer and viscosity modifier such as liquid foaming agents,volatile diluents for the plastisol and the like, or any similar mixtureyielding a plastisol of free-flowing features.

Usually, in making up the plastisol, it is advantageous to add a smallamount of metal soap such as aluminum stearate or barium and cadmiumsoaps as a dispersing agent to aid in maintaining the resin particles insuspension priOr to foaming. Similarly, if desired, pigments, fillers orstabilizers for the vinyl resins may be employed in the plastisols tocontrol the color, stability or other properties of finished foam and insome instances the use of volatile thinners such as are used inorganosols may be advantageous. Similarly, the liquid foaming agents ofthis invention can serve as thinners for the plastisol.

The foamable compositions of this invention are particularlyadvantageous, for they can be made up at one location for use at someother place at some later time. Moreover, if higher boiling normallyliquid foaming agents are employed, the compositions may be stored orshipped under atmospheric pressure. If the lower boiling agents are usedit is usually preferable to ship the compositions in sealed containerswhich will resist low pressures, particularly in summer months whenhigher temperatures may be encountered.

The relative amounts of the various constituents will, of course, varydepending upon the particular resin, plasticizer and foaming agentemployed and the density, plasticity and other properties desired in thefused foam. However, in general, when low density foams are desired, forexample, having densities of from about 1 to 10 pounds per cubic foot,the amounts of the constituents will be within the following limits:

Parts by weight Plasticizer 30 to Liquid foaming agent 10 to 25 Vinylresin 30 to 70 not considering the fillers, stabilizers, pigments, etc.,which are not critical in the composition. If higher density foamedproducts are desired, for example a shoe sole material which may have adensity of from 15 to 35 pounds per cubic foot, the relative amount offoaming agent may be decreased to as low as 2% by weight of thecomposition.

The foaming agent or agents of the present invention should bechemically inert to both the vinyl resin and the plasticizer andchemically stable at temperatures up to and including the fusingtemperature of the plastisol. If the foamable composition is to vbe heldfor any length of time before use, the foaming agent should have nosignificant solvating action on the vinyl resin in the plastisolalthough it can and often does decrease the viscosity of the plastisol.Desirably, the [foaming agent should be rm'scible with or soluble in theplasticizer at least to a minor degree at the temperature at which thefoaming agent is admixed with the plastisol, although such is notcritical with all of the foaming agents encompassed in this invention.

The polyhalogenated saturated hydrocarbons having atmospheric boilingpoints between about minus 40 F. and below plus 175 F. have beendiscovered in this invention to provide these superior plasticized vinylfoams. Thus, these polyhalogenated hydrocarbons can be normally liquidor normally gaseous compounds, and can be employed in either the liquidor gaseous state.

The physical and chemical properties of the foaming agents are quiteimportant with regard to the manner in which the process is conducted.The normally liquid agents having atmospheric boiling points of at leastambient or room temperature can be conveniently added to the plastisolor plasticizer without resorting to super-atmospheric pressure tomaintain it in the liquid phase. Furthermore, the boiling point must beconsiderably lower than the fusing temperature of the plastisol so thatexpansion and cell or pore formation will occur prior to fusion andsolvation as the temperature is raised from room temperature to thefusing temperature of the plastisol. Most vinyl resin plastisols fusebest at temperatures in the range of 300 F. to 400 F., and it isdesirable to employ a liquid foaming agent boiling at least about 150 F.below the fusing temperature. Thus, the normally liquid foaming agentsshould usually have an atmospheric boiling point below about 175 F.

In distinct contrast to the prior process which utilized gases boilingat very low temperatures from 46-2 F. for helium to l09 F. for carbondioxide, a gaseous foaming agent of this invention having an atmosphericboiling point of not less than about --40 F. nor much higher than thetemperature of the plastisol at the time of foaming must be employed.The radical difference between the present process aud the prior processis more readily appreciated by referring to the difference intemperature between the boiling point of the gaseous foam ing agent andthe temperature at which the plastisol is admixed with the gas. In thepresent process with these polyhalogenated saturated hydrocarbons, theplastisol temperature during admixture will generally be not more thanabout 120 F. above the atmospheric boiling point of the gas. In theprior process the gaseous agents boiled at temperatures between about500 F. to 150 F. below the mixing temperature.

The following polyhalogenated saturated hydrocarbons are representativeof suitable foaming agents for the process of this invention:

Atmospheric Gaseous Foaming Agent Pressure Boiling Point, F.

monochloro difluoro methane (Freon 22) -41 dichloro difluoro methane(Freon 12) 21 1, 2 dichloro 1, 1, 2, 2, tetrafluoro ethane (Freon 114)+38 1,1,1 trichloro 2,2,2 trifiuoro ethane +45. 8 dichloro monofiuoromethane (Freon 21) +48 1,2 difluoro ethane +50 1,1 dichloro ne +57. 31,1,1 trichloro e n +74. 1 trichloro monofluoro methane (Freon 11) +74.7 methylene chloride +104. 5 carbon tetra chloride +17(] The abovelisting is to be regarded in exemplification and not restriction to theuseful compounds. Bromine and iodine substituted polyhalogenatedcompounds having similar boiling points can likewise be used in thisprocess, as well as other polyhalogenated saturated hydrocarbons notlisted above. The preferred compounds of this invention are thenon-toxic, non-explosive and non-inflammable inert agents which have atleast two aliphatic carbon atoms and from 2 to 6 inclusive halogen atomsattached to said carbon atoms, We find it much simpler, however, toemploy non-hazardous agents such as the Freons which are readily andcommercially available at low cost. Incidentally, since greater amountsof the higher molecular weight agents are required to produce a givenvolume of gas, it is frequently less expensive to use smaller amounts ofa lower molecular weight agent which may be more costly than a heavieragent on a weight basis.

Briefly described this process involves the following steps:

l) Admixing the polyhalogenated hydrocarbon foaming agent into the fluidplastisol at a temperature below the solvation or fusing temperature ofthe resin in the plasticizer, and if desired, under pressure greaterthan atmospheric but less than about p.s.i.g.;

(2) Changing the ambient conditions on the thusformed admixture, i.e.,releasing the pressure and/ or heating the admixture, to form athree-phase fluid form;

(3) Forming the fluid foam into a desired shape such as by flowing itonto a moving conveyor belt or into suitable mold, which step can be, ifdesired, simultaneous with the step of changing ambient conditions;

(4) Heating the foam to the solvation or fusing temperature of theplastisol (300 F. to 400 F.) to effect solvation of the resin into theplasticizer, such as by transfer of heat to the foam as in oven heatingor by generation of the heat within the foam as in high frequencydielectric heating;

(5) Cooling the fused foam to a lower temperature at which it isform-retaining for removal from the mold or belt.

Prior to the fusing step, the foam is normally a threephase system,namely, liquid plasticizer which can contain a certain amount ofdissolved foaming agent, depending upon the solubility thereof,undissolved minute bubbles of foaming agent dispersed throughout theplasticizer, and particles of resin suspended in the plasticizer. Atthis stage, depending upon the relative solubility of the foaming agentand the fineness of the bubbles, the fluent mass may appear as a creamyfoam much like whipped cream or an almost clear liquid. There are,however, two techniques for effecting the solution of the foaming agentin the plasticizer to form the composition of our invention, whichtechniques are quite simple to carry out and make it possible to form astable plastisol-foaming agent composition which will successively foamand fuse to produce the desired structure upon heating. These techniquescan be roughly termed the liquid phase admixing and the gaseous phaseadmixing. In the liquid phase technique, either of two relatively simplemethods may be used. The first method is to maintain the foaming agentin liquid phase at a temperature below its atmospheric boil-ing pointand then add the liquid agent to the plasticizer or plastisol which may,if desired, be at a higher temperature. As the liquid agent goes intosolution its temperature increases and approaches the plasticizertemperature, but it is simultaneously diluted so that its vapor pressureis decreased to such extent that the combined vapor pressure of theplasticizer-foaming agent solution is less than atmospheric. The secondarrangement is also simple but requires a closed mixing vessel foreflecting solution. The plastisol or plasticizer is charged into themixing vessel along with foaming agent under sufficient pressure tomaintain the agent in the liquid state. As solution of the foaming agentoccurs the pressure in the vessel decreases to such extent that theresultant liquid oan be withdrawn to a zone of atmospheric pressure anddoes not foam until heated above room temperature. Dichloro monofluoromethane (Freon 21) is a very satisfactory agent to employ in thismanner, and it may be dissolved in the plasticizer either before orafter the plastisol is formed.

In certain instances where a highly soluble foaming i '3 agent boilingclose to atmospheric pressure is added to a plastisol, the novelcomposition of the present invention may result if the foaming agentsolubility is such that it completely dissolves in the plasticizer toproduce a twophase system free from bubbles.

Thus, it is seen that it is not necessarily critical in this inventionthat the foamable composition be solely two phase or solely three phase.

The solubility of the foaming agent in the plastisol plays an importantpart in the process of this invention and the improved results achievedthereby. For example, tests show that carbon dioxide is only veryslightly soluble in conventional plastisols (about 0.7 gram of carbondioxide can be dissolved in 1000 grams of a dioctyl phthalate-n-butylbenzyl phthalate-polyvinyl chloride plastisol). In contrast, forexample, dichloro difluoro methane (Freon 12.) is soluble in the sameplastisol under the same conditions of temperature and pressure to theextent of 9.7 grams per 1000 grams of plastisol and accordingly is about15 times as soluble as carbon dioxide. The higher boiling foaming agentssuch as 1,1 dichloro ethane and trichloro monofluoro methane have evengreater solubilities, and the superiority of this process and theproducts thereof over the prior process and products may well resultfrom the greater solubility of the gases.

The gaseous technique of this invention is particularly useful for thenormally gaseous foaming agents having higher atmospheric boilingpoints, but is also usable for normally liquid agents. In this.procedure the foaming agent can be incorporated into plastisolsmaintained either above or below the atmospheric boiling point of thegaseous agent, as part liquids or all gas or under pressure or not, asdesired. The usual gas procedure is to vaporize a portion of the foamingagent and provide a supply of the foaming gas under pressure. This gasmay be conducted to a mixer containing the plastisol and admixedtherewith. If the temperature of the plastisol is sufiiciently low thegas may dissolve completely to form a two-phase system (liquidplasticizer containing dissolved foaming agent and solid resinparticles). On the other hand, if the temperature is higher a threephasesystem such as is described above may be formed. If a two-phase systemis formed in which the vapor pressure of the dissolved agent is greaterthan atmospheric pressure the composition will form a three-phase foamupon a change of the ambient pressure, i.e., reduction of the pressureto atmospheric.

In contrast, if the vapor pressure of the dissolved agent is less thanatmospheric pressure a foam will not be formed upon reduction of thepressure to atmospheric but may be formed by changing the ambienttemperature, i.e., heating the plastisol. The formation and utilizationof such two-phase systems or compositions in the production of cellularproducts is readily conducted at atmospheric pressure by merely admixingthe liquid agent and the plastisol in a suitable vessel.

The liquid foaming agent is preferably added to the plastisol, but incertain instances, as where a more viscous plasticizer or plastisol isto be employed, it may be advantageous to incorporate all or a portionof the liquid foaming agent in the plasticizer prior to dispersing theresin in the plasticizer. The relative amount of the foaming agentincorporated in the plasticizer is important, as it is determinative ofthe density of the finished material. In most instances the amount offoaming agent should be between about and about by weight of the totalplastisol and foaming agent weight, although as previously stated, itmay be as low as 2% by weight of the composition. This relative amountof the liquid foaming agent to be used may be readily calculated byusing as the volume of each pound mol of agent 359 cubic feet, andcomputing the number of mols required per pound of plastisol to give thedesired density. Thus, the weight of foaming agent required depends uponthe molecular weight of the particular agent and the density desired inthe foam. Usually, the amount required will be slightly above thecalculated amount, i.e., within the range of about 10% to 30% greaterthan the quantity calculated to produce the requisite volume in thefoamed and fused resin because of losses and leakage in the process.

It is desirable that when employing the liquid foaming agents, the agentbe soluble in the plasticizer at least to such extent that all of thefoaming agent employed will be dissolved at the time of admixture withthe plastisol or plasticizer, as the case may be. If complete solutiondoes not occur, droplets of liquid foaming agent may be present in theplastisol, and when it is heated to form cells the droplets may suddenlyvaporize as they reach the boiling point of the foaming agent. This isundesirable and causes rejects of molded articles, for such suddenformation of relatively large masses of vapor within the very fluidplastisol produces large voids or blemishes in the finished foam insteadof a uniform, well distributed cell structure. By the same token,droplets of water, which are immiscible in the plasticizer, may producethis effect, and are to be avoided.

On the other hand, with the foaming agent completely dissolved in theplasticizer, the emergence of the vapor bubbles is very gradual as thetemperature rises, for the vapor pressure of the dissolved foaming agenttends to be a function of both the temperature and the relativeconcentration of the foaming agent in the plasticizer. Thus, as thetemperature rises the vapor pressure of the dissolved foaming agentrises until some of it exceeds the ambient pressure. Then somevaporization occurs, but this vaporization tends to reduce theconcentration of the foaming agent in the plasticizer, tending to lowerthe vapor pressure exerted. In this manner the foaming agent vaporizesquite slowly from the plasticizer forming the desired cellular or porousstructure in the plastisol.

Thus, as is seen, the change in ambient conditions on the foamablecomposition forms a three phase system of gas bubbles entrapped in theliquid plasticizer in which the solid resin is suspended. Contrary tothat system employed with other gaseous foaming agents, the three phasefoamed composition of this invention is free-flowing and does not haveto be sprayed or atomized into the molds when shaped cellular objectsare made. Another significant advantage of the free-flowingcharacteristics of the foamed composition is the self-leveling nature,which in open mold applications yields a porous surface whereas withnon-self-leveling foams, the surface must be scraped by doctor blade orotherwise which tends to collapse the foam on the then-formed surfaceand produce a skin elfect significantly different from the open cellsurface of these lfoams.

Curing or fusing of these foamed compositions is accomplished by heatingto elevated temperatures, at least sufficent to effect solvation of theresin in the plasticizer and gel the plastisol. The gelling retains thefoamed cellular structure of the composition and further heating fusesthe resin. Quite often there is only a minor temperature differentialbetween the gelation and fusion temperature, and most often thesetemperatures are within the range of 300-400 F although some latitude ofgelation and fusing temperature of the plastisol is to be expected,depending upon the particular plasticizer, the resin, and the solvatingtemperature of the resin in the plasticizer.

Although the invention has been described in a number of specificembodiments, it is to be understood that variations thereof may bepracticed without departing from its spirit or scope.

This application is a continuation of applications Serial Nos. 541,063and 541,064, both filed October 17, 1955, and now abandoned.

The following specific examples are illustrative of the novel processand composition of our invention. Unless otherwise specified, all partsare parts by weight.

8 Example I A plastisol was prepared containing the followingsubstances:

n-Butyl benzyl phthalate (Santicizer-l60, Monsanto) 250 Barium-cadmiumsoap (Barca 10) 10 A charge of this plastisol at 70 F. was placed in apressure vessel equipped with an agitator and gaseous dichloro difluoromethane (Freon 12) was introduced into the vessel at a pressure of about60 pounds per square inch gage. The agitator was operated, and as thegas dissolved and was dispersed in the plastisol, additional gas wasintroduced to maintain the 60 pounds per square inch gage pressure.During this mixing the plastisol temperature remained about 70 F. Thedifference between the foaming pressure (60 p.s.i.g.) and the saturatedvapor pressure of the gas at foaming temperature (70 p.s.i.g.) was about10 pounds per square inch. The time of mixing was about five minutes,and at the end of this time the gas inlet valve was closed and an outletvalve at the bottom of the vessel was opened to allow the gas pressureto blow the resultant foam out of the pressure vessel as it wasrequired. The unfused foam was an extremely stable free-flowing creamyliquid. This foam was charged into' rectangular open molds to a depth ofabout 'one quarter inch and was then fused in a dielectric heatingapparatus by rapidly heating to a temperature of about 325 F. Aboutone-half minute was required to raise the foam temperature to 325 F. Thefused foam was found to have an excellent cellular structure and adensity of 5.2 pounds per cubic foot. Similar samples were fused in anordinary oven maintained at 325 F. for fifteen minutes. The density ofthese samples was about five pounds per cubic foot. The resiliency ofall the samples was such as to render the material excellent for use inseat cushions, mattresses or the like.

Example II To obtain a comparison with the prior process, the method ofExample I was repeated using carbon dioxide as the foaming agent. Thegas pressure during mixing was 250 pounds per square inch gage. Allother conditions were identical with those of Example I. The density ofthe fused foam was 9.0 pounds per cubic foot. Thus, it will be apparentthat the fused foam density was about twice as great using carbondioxide as the foaming agent as with dichloro difluoro methane despitethe fact that about four times the pressure was used for the carbondioxide. The difference between the foaming pressure and the saturatedvapor pressure of the gas at foaming temperature was about 700 poundsper square inch, and the quantity of carbon dioxide required was manytimes the amount of the foaming agent of Example I.

Example Ill The method of Example I was repeated using dichloro difluoromethane (Freon 12) as the foaming agent at a pressure of 100 pounds persquare inch gage. This somewhat higher pressure was obtained by warmingthe cylinder containing the foaming agent to a temperature of about 95F. Thus, the gas as initially introduced into contact with the plastisolwas warmer than the plastisol, and it in effect liquefied and dissolvedsimultaneously in the cooler plastisol, for its saturated vapor pressureat 70 F. was less than the applied pressure. This is a convenient methodof obtaining solution of large quantities of foaming agent in theplastisol. As in Example I the time of mixing was about five minutes,and during mixing the plastisol temperature remained about 70 F. At theend of the mixing period the mixer outlet valve was opened and the thustreated plastisol was filled into molds. As

the plastisol'emerged the dissolved foaming agent vaporized to form afree-flowing foam. The filled molds were subjected to dielectric andoven heating as in Example I to effect fusion in two different ways. Thedensity of the fused foam was about 3.5 pounds per cubic foot regardlessof the fusing method.

Example IV The procedure of Example III was carried out upon a somewhatdifferent plastisol formed of the following:

Parts Polyvinyl chloride (Geon 121) 500 Dioctylphthalate 200 n-Butylbenzyl phthalate 200 Barium-cadmium soap 10 This plastisol contained 20%less plasticizer than the plastisol of Example III and was more viscous.The resulting fused foam had a good cell structure but much higherdensity than the fused foam of Example III. The foam density of thesamples formed from the less viscous plastisol ranged from 7.8 to 10pounds per cubic foot.

Example V The method of Example I was repeated except that thetemperature of the plastisol was maintained at 87 F. The gas pressurewas sixty pounds per square inch gage as in Example I. The fused foamwas found to have a density of 8.5. By comparing the results of thisexample with those of Example I it will be seen that the temperature ofthe plastisol at the time of gas incorporation-has a considerable effectupon the fused foam density. Generally, the lower the plastisoltemperature during mixing the more gas which is incorporated therein andthe lower the density of the fused foam.

Example VI The process of Example I was repeated using ammonia as thefoaming agent instead of dichloro difluoro methane. The applied pressureduring mixing of the agent and the plastisol was about p.s.i.g. Thefused foam had a density of about five pounds per cubic foot. The fumesof the ammonia were found to be very noxious and had to be ventedoutside the building. The use of ammonia is not generally satisfactorybecause of the difficulties in venting these fumes which are releasedfrom the unfused foa-m as well as during fusing. Moreover, it has beenfound that unfused foam formed by admixing ammonia in a plastisol willnot keep as well as unfused foams formed with halogen substitutedhydrocarbons as foaming agents. Example VII Example VIII The method ofExample VII was repeated using monochloro difluoro methane (Freon 22)and the same temperature and pressures as in that example. The fusedfoam had a density of 6.6 pounds per cubic foot when the gas dispersionstep was conducted at 50 p.s.i.g. and again higher pressures resulted ineven less dense fused foam.

Example IX The plastisol of Example I was pumped at a rate of aboutfifty pounds per hour through an annular passage heat exchanger havingan outer jacket space to which liquid ammonia refrigerant was supplied.The annular passage was formed by a cylindrical heat transfer wall, theexterior of which was in contact with the liquid ammonia, and arotatable mutator shaft, equipped with scraper blades which continuallyremoved chilled plastisol from the heat transfer wall, was rotated at ahigh speed. The plastisol entered the annular passage at one end at atemperature of about 80 F. and emerged from the other end at atemperature of about 30 F. Dichloro difiuoro methane (Freon 12) wasinjected into the annular passage at the inlet end at sufiicientpressure to maintain a back pressure within the annular space of about45 to 65 p.s.i.g.

During passage through the annular space, which was about 12 inches inlength, the plastisol and gas were thoroughly mixed to form a stablefoam which emerged con tinually from the outlet end and was filled intomolds as in Example I. The foam in the filled molds was fused as inExample I and excellent fused foams having densities as low as aboutthree pounds per cubic foot were obtained.

The operating conditions were varied in order to produce differentdensities in the fused foams. The following table gives the operatingconditions and results for The apparent lack of correlation betweenfused foam density and back pressure or outlet temperature is due to thefact that density was controlled primarily by varying the rate ofaddition of the gas. This produced concomitant variations in temperatureand back pressure. It was found that very good control of productdensity can be achieved conducting the operation at a predetermined backpressure and outlet temperature and varying the rate of gas supply.

When foams having densities greater than about six pounds per cubic footwere produced, the cooled plastisol-gas mixture was found to emerge muchas a liquid rather than a foam. The gas was very finely dispersed invirtually invisible bubbles, and, apparently, no gas was liberated fromthe plastisol foam either prior to or during fusing. At lower densities,the bubbles were larger and the mixture appeared to be more of a truefoam, but still the amount of gas lost from the foam prior to and duringfusing was extremely slight compared with the losses experienced withthe prior carbon dioxide process.

Example X The following materials were mixed to form a plastisol in theconventional manner:

Parts Vinyl chloride resin (Vipla P) 500 Dioctyl phthalate 375 Tricresylphosphate 125 Barium-cadmium soap (Barca 10 Next, the plastisol foam waswithdrawn from the mixing vessel through a screen equipped nozzle andfilled into molds which were placed in a dielectric heating apparatusfor fusing. Fusing was effected by rapidly heating the foam to about 350F. The cooled, fused foam was removed from the molds and the density wasmeasured. The density was found to be from 4.9 to 6.3 pounds per cibicfoot. The cell structure was very fine. Similar tests made withplastisols consisting of the same plasticizers in comparable amounts butdifferent polyvinyl chloride resins, namely, Solvic 334, Corvic 65/42and Corvic PM produced satisfactory fused foams but the densities wereconsiderably higher, as follows:

Lbs/cu. ft. Solvic 334 9.5 to 10.7 Corvic 65/42 16.1 to 17.2 Corvic PM10 to 12 Equal parts of Corvic 65/42 and Corvic PM 9.9 to 10.6

Example X] A plastisol was prepared by the conventional method from thefollowing materials:

Parts Polyvinyl chloride (Geon 121) 500 Dioctyl phthalate 250 n-Butylbcnzyl phthalate (Santicizer #160, Monsant-o) 250 Barium-cadmium soap(Barca 10) 10 Five hundred parts by weight of this plastisol were mixedin a simple open top mixer for several minutes at room temperature toinsure uniform distribution of the resin particles in the mixture. Next,about seventy-five parts by weight of liquid trichloro monofluoromethane (Freon 11) foaming agent (temperature about 70 F.) were addedand mixed for about three minutes to insure thorough mixing with thefluid plastisol. The resulting composition had a somewhat cloudyappearance due to the presence of the dispersed resin particlessuspended in a single liquid phase since the foaming agent andplasticizer were miscible.

Then the plastisol and foaming agent composition was filled into moldsdirectly from the mixer, and various methods of fusing were employed.

The best results from the standpoint of density were obtained by firstplacing the filled molds in an externally heated oven, maintained at atemperature at 250 F. The molds were left in this oven for five minutes.During this period the volatile foaming agent slowly vaporized and thecomposition increased in volume, much like the rising of a loaf ofbread, to an expanded but unfused foam. The volume of the expandedcomposition at the end of the oven heating period was about ten timesthe volume of the composition prior to heating. This high degree ofexpansion was possible because the composition was unfused and theliquid phase plasticizer was relatively fluid indicating that slight, ifany, solvation of the suspended resin particles had occurred.

Following the five minute oven heating or preheating step, each mold wasremoved from the oven and placed in a Thermax Model 7R dielectricheating apparatus, manufactured by the Girdler Company, Louisville,Kentucky, where a high frequency alternating current field Was utilizedto very rapidly heat the entire expanded mass to a fusing temperature ofabout 350 F. At this temperature complete solvation of the resin in theplasticizer occurred and, upon cooling, the desired fused cellularstructure vinyl resin resulted. The material was removed from the moldsand was found to have a uniform cell structure with predominatelyinterconnecting or open cells and very good resiliency so as to besuitable for seat cushions, mattresses and the like.

The densities of the foamed product from a number of molds processed asoutlined were measured and found 13 to average about 6.5 pounds percubic foot. The lowest density sample was 5.7 pounds per cubic foot.Samples of the same initial composition preheated at temperaturesranging from 200 F. to 240 F. for periods of to minutes exhibitedslightly higher densities ranging from about 7 to 9 pounds per cubicfoot.

Molds which were filled with this composition and placed in thedielectric heating apparatus for rapid heating from room temperature to350 F., without preheating to produce an initial expansion, were foundto produce a much more dense material with only fair cells indicatingthat the slow preheating step is quite advantageous particularly wherelow density is desired. The fusing of such compositions by heating in anoven from room temperature to fusion temperature of from 300 F. to 400F. with elimination of the rapid dielectric heating step is effective inproducing low density fused products because oven heating is essentiallyslow and expansion can occur during the initial stages before the fusionand solvation commences. However, for thicker sections the two steparrangement is preferred because the poor heat conductivity of the foammay result in fusion and solvation of the outer portions of the massbefore complete expansion of the interior has occurred, and this islikely to result in a non-uniform structure. The initial preheat ispreferably carried out in an oven, but, if desired, a dielectric heatingapparatus may be used to heat the material stepwise first to lowertemperatures for complete expansion while in a fluid state and finallyto fusing temperature.

Example XII To five hundred parts by weight of the plastisol of ExampleXI varying amounts of liquid trichloro monofluoro methane (Freon 11)were added in order to determine the optimum quantity of this foamingagent to use. Forty-five parts by weight of liquid agent produced a faircell structure and expansion when an oven preheat of three minutes at275 F. followed by dielectric heating to 350 F. was employed. Theproduct density was 5.6. This composition, however, gave negativeresults in other instances with very little expansion and poor cellstructure.

Similar plastisol compositions wih' fifty-eight parts by weight of theliquid foaming agent to five hundred parts of plastisol produced goodresults with a five minute 250 F. preheat and a dielectric heatingfusing at 350 F. Densities were slightly higher ranging from 7.2 to 9.6but cell structure was much better than in the case of the compositionsemploying forty-five parts by weight of foaming agent.

One hundred fifteen parts by weight of the liquid foaming agent weremixed with four hundred parts of plastisol, and the composition wasfused using an oven preheat. The fused foam density was about sevenpounds per cubic foot, but the cell structure was not as good as infoams produced from compositions containing less foaming agent.

The best results were obtained utilizing sixty-five parts by weight ofliquid foaming agent to five hundred parts of plastisol. The preheat wasfrom four to five minutes in a. 250 F. oven, and it was followed bydielectric heating to about 350 F. for about one minute. A post fusingstep consisting of maintaining the fused foam at a temperature of 310 F.for seven minutes before cooling to room temperature was also employed.This preferred expansion and fusion procedure is very well adapted to becarried out on a continuous basis by passing filled molds on a conveyorfirst through a preheat oven, then through a dielectric heating zone andfinally through a post fusing oven.

Where it is desired to produce a continuous sheet of foam thecompositions of this invention may be flowed on to an endless belt andconveyed through heating apparatus for time and temperature controlledheating and v the fused foam sheet stripped off at the belt uponemerfollowing a 250 F. oven preheat.

geuce from the heating zone, either before or after complete cooling hasoccurred.

Example XIII The plastisol of Example XI was mixed with liquid methylenechloride (CH CI Forty-two parts by weight of the liquid agent to fivehundred parts of plastisol were utilized, and the composition was fusedat 350 F. following a five minute oven preheat at 250 F. A fused foamhaving a high density and a rather poor cell structure was produced.

Compositions containing about seventy parts by weight of methylenechloride for each five hundred parts of plastisol produced similarresults both with a five minute 250 F. oven preheat followed by adielectric fusion and with the preheat step eliminated.

Compositions containing about one hundred parts of methylene chloridefoaming agent for each five hundred parts of plastisol (about 20% byweight) produced foams having fair cell structure and having densitiessomewhat higher than those obtained utilizing dichloro monofluoromethane (Freon 11) as the foaming agent and optimum fusing conditions.Best results were obtained with a 250 F. five minute oven preheat.

Example XIV Eighty parts by weight of carbon tetrachloride were admixedwith five hundred parts by weight of the plastisol of Example XI anddielectrically fused at 350 F. Fused foam having a high density and arather poor cell structure was obtained. These results indicate that thelower boiling foaming agents tend to produce less dense foams havingbetter cell structure, but that the higher boiling agents such as carbontetrachloride which boils at about F. are suitable if higher densitymaterials are desired.

What is claimed is:

1. A composition suitable for forming an expanded vinyl resin foam ofcellular structure upon heating including a vinyl resin plastisolcomprising a finely divided vinyl resin containing a predominant amountof vinyl chloride polymerized therein and suspended in an organicplasticizer for the said resin; and a foaming agent for the saidplastisol comprising a polyhalogenated saturated hydrocarbon having anatmospheric boiling point between about 40 F. and about F. and beingchemically inert with respect to the plasticizer and the vinyl resin,and being substantially completely soluble in the said plasticizer whenin the liquid state.

2. The composition of claim 1 in which the various 3. The composition ofclaim 2 in which the average size of the vinyl resin particles isbetween 0.02 and 2 microns in diameter.

4. The composition of claim 2 in which the vinyl resin contains from 60to 100% by weight of vinyl chloride polymerized therein.

5. The composition of claim 2 wherein the vinyl resin is polyvinylchloride.

7 6. The composition of claim 2 in which the polyhalogenated saturatedhydrocarbon has at least two carbon atoms per molecule, and between 2and 6 inclusive halogen atoms bonded to said carbon atoms.

7. A composition suitable upon heating for forming an expanded vinylresin foam of solid cellular structure, said composition being atwo-phase system, the liquid phase comprising an organic plasticizer andat least one polyhalogenated saturated hydrocarbon having an atmosphericboiling point below about 175 F. dissolved in said plasticizer, and thesolid phase'of said system comprising a finely divided vinyl resincontaining a predominant amount of vinyl chloride polymerized therein,said resin being suspended in the liquid phase in amounts to provide afree-flowing fluid plastisol, foamable upon heating to elevatedtemperatures.

8. The composition of claim 7 in which the various ingredients arepresent in the following proportions:

Parts by weight Plasticizer 30 to 70 Polyhalogenated saturatedhydrocarbon 10 to Vinyl resin to 70 9. The composition of claim 8 inwhich the vinyl resin contains between 60 to 100% by weight of vinylchloride.

10. The composition of claim 8 wherein the vinyl resin is polyvinylchloride.

11. The composition of claim 8 in which the polyhalogenated saturatedhydrocarbon has at least two carbon atoms per molecule and between 2 and6 inclusive halogen atoms bonded to said carbon atoms.

12. A composition suitable upon heating for forming an expanded vinylresin foam of solid cellular structure, said composition being athree-phase system, the solid phase of said system comprising a finelydivided vinyl resin containing a predominant amount of vinyl chloridepolymerized therein, said resin being suspended in a liquid phase, andsaid liquid phase comprising predominately an organic plasticizer forsaid vinyl resin and a vapor phase comprising at least one vaporizedpolyhalogenated saturated hydrocarbon having a boiling point above aboutF.

13. The composition of claim 12 in which the various ingredients arepresent in the following proportions:

Parts by weight 14. The composition of claim 13 in which the vinyl resincontains between to by weight of vinyl chloride polymerized therein.

15. The composition of claim 13 in which the vinyl resin is polyvinylchloride.

16. The composition of claim 13 in which the polyhalogenated saturatedhydrocarbon has at least two carbon atoms per molecule and between 2 and6 inclusive halogen atoms bonded to said carbon atoms.

17. A process of forming foamed vinyl resin of solid cellular structurewhich comprises dispersing in a freeflowing plastisol maintained at atemperature substantially below its fusion temperature and at a pressurebelow 100 p.s.i., said plastisol including a finely divided vinyl resincontaining a predominant amount of vinyl chloride polymerized thereinand an organic plasticizer for said resin, a polyhalogenated hydrocarbonhaving an atmospheric boiling point between about 40 F. and about F. andbeing chemically inert with the resin and the plasticizer, and beingsubstantially completely soluble in the said plasticizer when in theliquid state forming a free-flowing, expanded, low density foam from themixture by exposure to a temperature substantially above the atmosphericboiling point of the said polyhalogenated hydrocarbon, heating the lowdensity foam to at least the fusion temperature of the plastisol toeffect solvation of the resin in the plasticizer and fuse theplasticized resin and then cooling the fused foam to form the foamedvinyl resin of solid cellular structure.

18. The process of claim 17 in which the vinyl resin contains from 60 to100% by weight of vinyl chloride polymerized therein.

19. The process of claim 17 in which the vinyl resin is polyvinylchloride.

20. The process of claim 17 in which the poly-halogenated saturatedhydrocarbon has at least two carbon atoms per molecule and from 2 to 6,inclusive, halogen atoms bonded to said carbon atoms.

21. The process of forming a vinyl resin foam of solid cellularstructure which comprises forming a two-phase system including as theliquid phase, a liquid organic plasticizer and a polyhalogenatedsaturated hydrocarbon having an atmospheric boiling point between about40 F. and about +17'5 F. dissolved in the plasticizer and as the solidphase, finely divided solid particles of a vinyl resin containing apredominant amount of vinyl chloride polymerized therein, said solidresin particles being suspended in said liquid phase, changing theambient conditions on said two-phase system to vaporize thepolyhalogenated saturated hydrocarbon and form a three-phase fluid foam,applying additional heat to effect solvation of the resin particles inthe plasticizer forming a two-phase foam of plasticized vinyl resin andvaporized polyhalogenated hydrocarbon and fuse the said plasticizedresin and then cooling the resultant cellular mass to form said vinylresin foam of solid cellular structure.

22. The process of claim 21 in which the vinyl resin contains between 60and 100% by weight of vinyl chloride polymerized therein.

23. The process of claim 21 in which the polyhalogenated saturatedhydrocarbon has at least two carbon atoms and between 2 and 6,inclusive, halogen atoms bonded to said carbon atoms.

24. A process of forming foamed vinyl resin of solid cellular structurewhich comprises dispersing a polyhalogenated saturated hydrocarbonfoaming agent in gaseous state and from an external source in afree-flowing plastisol maintained at a temperature substantially belowits fusion temperature, the dispersing of said foaming agent in theplastisol being carried out at a pressure less than 100 p.s.i., saidplastisol including a vinyl resin containing a predominant amount ofvinyl chloride polymerized therein and an organic plasticizer for saidresin, said foaming agent having an atmospheric boiling point aboveabout 40 F., next expanding the plastisol by reducing the pressurethereon to produce a free-flowing, low density, three-phase fluid foam,heating the low density fluid foam to the fusion temperature of theplastisol to effect solvation of the resin in the plasticizer, and thencooling the fused foam to form the foamed vinyl resin of solid cellularstructure.

25. A process of forming foamed vinyl resin of solid cellular structurewhich comprises forming a free-flowing, three-phase system in which theliquid phase comprises a plasticizer for the resin, the solid phasecomprises minute particles of a vinyl resin containing a predominantamount of vinyl chloride polymerized therein and the gaseous phasecomprises a polyhalogenated saturated hydrocarbon having an atmosphericboiling point above about 40 F. and below about +175 F. and beingchemically inert with respect to the plasticizer and the resin, saidthree-phase system being formed at a pressure below about 100 p.s.i.g.and at a temperature substantially below the fusion temperature of theresin in the plasticizer, heating said three-phase system to said fusiontemperature to form a two-phase cellular system, and next cooling thetwo-phase system to a lower temperature to solidify the two-phasecellular system.

26. The process of claim 25 in which the solid phase of the three-phasesystem is a vinyl resin which contains between 60 and 100% by weight ofvinyl chloride polymerized therein.

27. The process of claim 25 in which the gaseous phase of the three-phase system is a polyhalogenated saturated hydrocarbon having at leasttwo carbon atoms per molecule and between 2 and 6, inclusive, halogenatoms bonded to the said carbon atoms.

28. A process for forming a resin foam of solid cellular structure whichcomprises dissolving in a vinyl resin 75 plastisol a volatilepolyhalogenated saturated hydrocarbon at least in partially liquid statebut at a pressure below 100 psi, said foaming agent having anatmospheric boiling point between about 40 F. and about +175 F. andbeing chemically inert with respect to the plastisol constituents,exposing the thus-treated plastisol to a temperature above the boilingpoint of the said foaming agent to form an expanded, free-flowingthree-ph ase fluid foam, then heating the fluid foam to the fusiontemperature of the plastisol to effect solvation of the resin in theplasticizer, and then cooling the thus-treated foam.

References (Iited in the file of this patent UNITED STATES PATENTSHarrison May 19, Stober Oct. 22, Taylor Sept. 18, Schwerke Jan. 12,Stastny et a1 June 15, Dennis Sept. 18, Hawkins Aug. 25,

17. A PROCESS OF FORMING FOAMED VINYL RESIN OF SOLID CELLULAR STRUCTUREWHICH COMPRISES DISPERSING IN A FREEFLOWING PLASTISOL MAINTAINED AT ATEMPERATURE SUBSTANTIALLY BELOW ITS FUSION TEMPERATURE AND AT A PRESSUREBELOW 100 P.S.I. SAID PLASTISOL INCLUDING A FINELY DIVIDED VINYL RESINCONTAINING A PREDOMINANT AMOUNT OF VINYL CHLORIDE POLYMERIZED THEREINAND AN ORGANIC PLASTIZER FOR SAID RESIN, A POLYHALOGENATED HYDROCARBONHAVING AN ATMOSPHERIC BOILING POINT BETWEEN ABOUT -40* F, AND ABOUT+175* F, AND BEING CHEMICALLY INERT WITH THE RESIN AND THE PLASTIZER,AND BEING SUBSTANTIALLY COMPLETELY SOLUBLE IN THE SAID PLASTIZER WHEN INTHE LIQUID STATE FORMING A FREE-FLOWING, EXPANDED, LOW DENSITY FOAM FROMTHE MIXTURE BY EXPOSURE TO A TEMPERATURE SUBSTANTIALLY ABOVE THEATMOSPHERIC BOILING POINT OF THE SAID POLYHALOGENATED HYDROCARBON,HEATING THE LOW DENSITY FOAM TO AT LEAST THE FUSION TEMPERATURE OF THEPLASTISOL TO EFFECT SOLVATION OF THE RESIN IN THE PLASTIZER AND FUSE THEPLASTICIZED RESIN AND THEN COOLING THE FUSED FOAM TO FORM THE FOAMEDVINYL RESIN OF SOLID CELLULAR STRUCTURE.